Hand-guided appliance with an internal combustion engine with direct electronic injection

ABSTRACT

In a manually operated machine such as a chain saw or the like, an internal combustion engine (10) located in a housing (17) and having an associated fuel injection mechanism (70) and an electro-mechanical module (80) is used to drive the machine. The engine (10) is a two-cycle one having a fuel container (140) arranged in or on the housing (17). The fuel injection mechanism in addition to the fuel container includes an injection valve (20) and a connecting tube (21) connecting the fuel container with the valve. For the connection between the outlet (22) of the injection valve (20) and the engine (10), a capillary tube (27) is used whose cross-sectional diameter is at maximum five times the cross-sectional diameter of the outlet of the injection valve, and the capillary tube is formed into the shape of a spring with its outlet opening directed into the engine block. The electro-mechanical module (80) contains means (25) for producing the drive voltage and a control circuit (26) with which the injection valve (20) is electrically connected.

TECHNICAL AREA

The invention relates to a hand-operated tool, more particularly cuttingdisks, brush cutters or the like, with an internal combustion engine,preferably a two-stroke engine with electronic direct injection of thefuel, which is provided with a cooling fan disposed on the crankshaftand, within the area of the cylinder, with a cooling air guidance meanswhich brings about a flow along the crankshaft axis.

STATE OF THE ART

When fuel is injected into the internal combustion engine, it isattempted to perform this in such a way that a good mixture preparationwith a simultaneous optimization of the waste gas quality is achieved.

In the DE 41 42 354 A1, a tool is disclosed which possesses a block ofinjection pumps that is secured to a mounting plate separating theintake section for the combustion air from the engine space. However,this leads to an increased thermal stress of the injection pump blocksince the latter forms a compact unit with the mounting plate so thatthe waste heat from the engine space is passed on direct to the partscarrying fuel, whereby a gassing of the fuel results.

Also from the DE 37 35 711 A1, a hand-operated tool is known. In thistool, the injection pump is flexibly connected with the engine so as toavoid mechanical and thermal stresses acting upon the injection pump.But it is preciselythe flexible connection which harbours new problemsbecause the flexible pipeline makes an exact control difficult andsince, on account of it being routed through non-cooled regions--closeto the engine--the risk of the fuel being gassed likewise exists.

DESCRIPTION OF THE INVENTION

That is why the technical problem of the invention is to optimizetwo-stroke internal combustion engines of the type in question or theirfuel injection.

This technical problem is resolved by the features characterized in theclaim 1.

To this end provision is made according to the invention, particularlyin power chain saws wherein the cylinder is disposed so as to bearranged vertically or inclined relative to the chain blade axis, forthe intake chamber with the filter to be located on the side of thehandle and for the cooling blower or fan to be mounted on thecrankshaft, while a cooling air guidance means is allocated to thecylinder, this brings about a flow along the axis of the crankshaft, fora partition adjacent to the cylinder separating the continguous intakechamber from the cooling air guidance means and for disposing the fuelinjection valve above the inlet duct for the drawn-in air in thecylinder, by preference with an inclination toward the cylinder head andwhile penetrating the partition.

Preferably, an intake section secured to the cylinder with the inletduct, is constructed so as to overlap the fuel injection valve above theinlet duct and as a pressure element for the same.

According to a preferred embodiment, the intake section is equipped withcurrent supply contacts for the electronically controlled fuel injectionvalve, in which case the intake section can incorporate the fuel supplyor fuel evacuation for the electromagnetically controlled fuel injectionvalve.

Furthermore, the intake section may be provided with an air filterand/or an air guidance path with a device for cooling the fuel.

According to a further preferred embodiment, the intake section isequipped with a multipoint plug on an intake air housing, which alsoforms the partition to the cylinder, in the operational state it is inengagement, while the intake air housing possesses the controller forsupplying the internal combustion engine.

More especially a power chain saw, with an internal combustion engineand a fuel injection system is often intergrated into the housing of thetool, as well as the fuel tank and a supply container for lubricatingoil and the cooling air guidance means.

In fuel injection systems in motor vehicles it is known to dispose thepressure controller in the fuel tank direct or in the region of the fueldistribution on the engine in the engine space.

In a hand-controlled tool, in order to arrange the pressure controllerof the fuel pipe system of the fuel injection system of the internalcombustion engine in a favorable manner from a spatial, operational andcooling-technical point of view, provision is made according to theinvention for disposing the pressure control valve of the fuel injectionsystem in or on the fuel tank.

The pressure control valve is in this case preferably to be positionedin such a way that the same additionally projects into the distributorspace of the cooling air or is mounted in the same.

Advantageous further developments of the invention are characterized inthe subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiment examples of the invention are explained ingreater detail with the aid of the drawings. Thus:

FIG. 1 shows in a schematic view a first embodiment of a power chain sawwith the disposition of the pressure controller according to theinvention;

FIG. 2 shows in a schematic view a second embodiment of a power chainsaw with the disposition of the pressure controller according to theinvention;

FIG. 3 shows in a schematic view a third embodiment of a power chain sawwith the disposition of the pressure controller according to theinvention, and

FIG. 4 shows in a schematic view a fourth embodiment of a power chainsaw with the disposition of the pressure controller according to theinvention.

BEST WAY OF REALIZING THE INVENTION

The power chain saw 10 depicted in FIG. 1 is in a normal manner equippedwith an internal combustion engine not shown in greater detail in ahousing 11, a chain blade 12, a handle 13 and other fixtures.

On the top side 14 of the housing 11, the cylinder 15 projects, which,in the direction of the chain blade 12, supports an exhaust 16 and, inthe direction of the other side, a fuel injection valve 17 and an intakesection 18. Between the cylinder 15 and the fuel injection valve 17 aswell as the intake section 18, a bulkhead wall 19 is located, which isconstituted of an intake air housing 20 with the inlet duct 15a and theoutlet duct 15b and a cooling air housing 21 for the cylinder 15, inwhich case the intake air housing 20 is comprised of a housing cover 20aand the housing bottom 20b.

The fuel injection valve 17 is a disposed above the intake section 18 soas to be directed obliquely upwardly, while both devices penetrate thepartition 19.

The electronic controller 22 is mounted in the intake housing 20. Theintake section 18 is provided with an air filter 23. The throttle valveconnection piece 24 is additionally mounted in the intake section 18.

With the aid of the waste gas sensor 25 disposed within the area of theexhaust 16 or inside the outlet duct 15b of the cylinder 15, it ispossible to determine the waste gas temperature for the controller 22.

An optimal operational behavior is achieved when the fuel pump not shownin the drawing in or on the fuel tank 26, is disposed in the intake airstream 27 or in the cooling air stream 28.

The power chain saw 10 depicted in the FIGS. 2 through 4 is comprised ofa basic housing 11, on which a handle 13 and the chain blade 12 aredisposed. Inside the basic housing 11, the fuel tank 26, a supplycontainer for lubricating oil, the cooling air guidance means and theinternal combustion engine are located, which are not illustrated ingreater detail here as well as other normal means. Located on the basichousing 11 or, rather, projecting from the same, is the cylinder 15, onwhich the magnetic injection valve 31 as well as a means for the intakeof combustion air are disposed.

The fuel tank 26 is provided on the side 38 of the basic housing 11located opposite the chain blade 12 within the area of the handle 13.The pressure controller 35 is placed in the basic housing 11, to be moreprecise, in that part, in which also the fuel tank 26 is to be found.

In the embodiment depicted in FIG. 2, in the intake air housing 20mounted on the basic housing 11, the intake section 32 with the fuelreturn pipe 34, an electronic controller 30 and the magnetic injectionvalve 31 are disposed.

The pressure controller 35 of the fuel injection system is, according tothe invention, disposed externally on the fuel tank 26 in the intake airstream 36. The air stream 29 is produced by the magnet wheel/fan wheel28 and conducted from the basic housing 11 to the cooling air housing37.

In the embodiment illustrated in the FIG. 3, in contrast to theembodiment shown in the FIG. 2, provision has been made for the pressurecontroller of the fuel injection system to be disposed on the exteriorof the fuel tank 26 in the intake air stream 36 and this, according tothe invention, so as to project into the intake air housing 20.

In the embodiment depicted in FIG. 4 on the other hand, provision hasbeen made for the pressure controller 35 for the fuel injection systemto be disposed on the fuel tank 26, which is integrated into the basichousing 11.

LIST OF REFERENCE NUMBERS

Power chain saw 10

housing 11

chain blade 12

handle 13

top side 14

cylinder 15

cylinder inlet duct 15a

cylinder outlet duct 15b

exhaust 16

fuel injection valve 17

intake section 18

bulkhead wall 19

intake air housing 20

intake air housing, cover 20a

intake air housing, bottom 20b

cooling air housing 21

electronic controller 22

air filter 23

throttle valve connection piece 24

waste gas sensor 25

fuel tank 26

intake air stream 27

cooling air stream 28

magnet wheel/fan wheel 29

electronic controller 30

magnetic injection valve 31

intake section 32

fuel return flow pipe 34

pressure controller 35

intake air stream 36

cooling air housing 37

side 38

What is claimed is:
 1. A hand-guided tool with a two-stroke internalcombustion engine with an electronically controlled fuel injectionsystem having a fuel injection valve and a pressure controller, with acooling blower mounted on the crankshaft, with a cylinder with intakeand outlet ducts, and with a cooling air guidance means in the vicinityof the cylinder which brings about an air flow along the axis of thecrankshaft, wherein:a bulkhead wall runs along the cylinder andseparates an adjacent intake air housing with an air intake section fromthe cooling air guidance means, the intake air housing channels air intoan intake air stream when the engine is running, the fuel injectionvalve is disposed above the cylinder intake duct so as to penetrate thebulkhead wall, and said pressure controller of the fuel injection systemis located in said intake air stream.
 2. A hand-guided tool according toclaim 1, wherein:the fuel injection valve is installed so as to beinclined toward a cylinder head on the cylinder.
 3. A hand-guided toolaccording to claim 1, wherein:the fuel injection valve has an injectionduct located opposite the side of the outlet duct of the cylinder andabove the inlet duct of the cylinder.
 4. A hand-guided tool according toclaim 1, wherein: the intake section serves for accommodating the fuelhandled by the fuel injection valve.
 5. A hand-guided tool according toclaim 1, wherein:the intake section is provided with an air filter andan air guidance path with a means for cooling the fuel.
 6. A hand-guidedtool according to claim 1, wherein:the fuel injection valve projectsinto the intake air housing and, in the region of the bulkhead wall, isprovided with a sealing element.
 7. A hand-guided tool according toclaim 1, wherein:the bulkhead wall, within the region of the penetrationof the fuel injection valve, is configured with a convexity.
 8. Ahand-guided tool according to claim 1, wherein:the intake air housing iscomprised of a bottom and a cover, said cover carrying an electroniccontroller for the fuel injection valve.
 9. A hand-guided tool accordingto claim 1, wherein:the intake air housing is provided with the bulkheadwall.
 10. A hand-guided tool according to claim 1, wherein:the intakeair housing is, in its interior, provided with control wiring for thefuel injection valve.
 11. A hand-guided tool according to claim 1,wherein:the intake section serves to accommodate control wiring for thefuel injection valve.
 12. A hand-guided tool according to claim 1,wherein:a throttle valve connection piece is constructed so as toaccommodate an intake air temperature sensor.